Double-letter processing in developmental and skilled handwriting production: Evidence from kinematics.

In this study, we investigated the effects of double-letter processing on handwriting production in beginning and skilled writers of German. One hundred and thirty-seven children from Grades 2 and 3 and 31 adult participants were asked to copy words with double consonants (e.g., "Kanne") and matched words without double consonants (e.g., "Kante") from a computer screen onto a pen tablet, while their handwriting was recorded with high spatio-temporal resolution. Handwriting productions were analysed in terms of Reading Duration, Writing Onset Duration, and Letter Duration at the letter positions preceding or forming the onset of the corresponding consonant clusters. Our results showed that second graders take less time to initiate writing words with double consonants than words without double consonants, while both second and third graders take less time to read words with double consonants than words without double consonants. Critically, although second and third graders write down a letter faster when it corresponds to the first letter of a double-letter unit than a consonant cluster, it is the other way around for adults. We interpret these findings within extant theories of handwriting production and offer an explanation for the different nature of the effects observed in beginning and skilled writers.